This data has obvious utility to advertisers. But as Facebook’s enrollment grows to encompass effectively everyone and the company offers increasingly granular targeting filters — as of mid-July, advertisers can target users on their birthday! — the estimator tool itself may become a useful tool of market and social sciences research.

No doubt the estimator can uncover anomalies that warrant further investigation. Consider this one: Of the almost 24 million 20-somethings on Facebook (10,980,540 men, 12,899,180 women), the men are more than 50% more likely to describe themselves as “single” than women (33.6% of men vs. 21.7% of women). Presumably, the difference lies not in the reality — there are not that many more single men than women — but in what information these two groups want to expose about themselves. Are these young women leery of online suitors? Are these young men leery of commitment? (Alright, it’s not the most rigorous or interesting example, but you get the idea.)